Once your fingerprint is out in the wild, any future service that uses it as a means of authentication is already compromised before you've used it even once. That's why I think it's prudent to think twice before you frivolously use it on a toy - that's all.
It's compromised already, your fingerprints are everywhere. Mine are everywhere. It wouldn't be hard to follow someone and get prints. Any future use would require more than just a fingerprint anyway. Imagine an ATM where you only needed a fingerprint to get cash. You'd have hordes of people dusting for prints all over the place hoping to hit a jackpot.
As far as images of prints being stored I think it's safe to say that isn't how it's done. Imagine a vault that could only be opened if a book was placed in front of an optical character reader. Only one specific title will open the vault, and no one but the vault owner knows what that book is. If the OCR system had an image of all pages of the special book, it could be hacked and the image viewed to see which book was required... Too simple, but so is the solution. Instead of scans of the book, it simply contains the following:
Page 1: 45th character is t
Page 17: 6th character is F
Page 94: 204th character is p
Page 32: 15th character is .
Etc etc, maybe 100 of these entries.. whatever would be necessary to be statistically improbable to have two different books match. Now it would be impossible to recreate the text of the book. Even the OCR software doesn't know what the book is after a correct scan because it is just looking at those few points to verify. The only way an unauthorized individual could find out would be to scan every book in existence until they got a match, which really isn't relatable to fingerprints as it isn't practical to ask everyone to "touch this sensor for me to see if I can unlock the phone."
Now, to be true to your original question... I think if you mistrust Apple to the point where you believe they are flat out lying about the technology in question, it would be hard to trust some method a random forum user suggests to circumvent that technology. Perhaps foil backed electrical tape? But would that defeat a capacitance based system? Cover the stainless ring so it doesn't detect a finger? But perhaps that ring is just a ruse to fool people into thinking you can cover it and protect yourself? An option in settings? We already established a lack of trust so who says that option actually disables anything. That leads to other options such as gloves, a stylus, a knuckle (that seems like a good way).
I apologize if my book analogy doesn't fit exactly, I certainly don't have the background to know exactly how these systems work, I just do trust when they say you can't reverse the process and create a fingerprint from the data used to verify an acceptable print (which I've been hearing for over a decade on print systems I've had to use, although I suppose its possible they're all lying)
Good luck with whatever method you choose.